Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Integrated crop management strategies in Sahelian land use systems to improve agricultural productivity and sustainability : a case study in Mali

Auteur : Samaké, O.

Université de soutenance : Wageningen Universiteit

Grade : Doctor Thesis 2003

Részumé
Sustainability of food production in the Sahel of West Africa requires Integrated Crop Management (ICM) strategies including different technologies that take into account constraints of stakeholders at different scale levels. To achieve this objective, combined effects of growing cowpea after different fallow durations followed by millet sole crop or intercropped with cowpea, and application of P-fertilizers were quantitatively evaluated. Prior to implementation of the experiments, a multi-scale characterization was adapted to determine major opportunities and constraints to millet production. The method used so far has been mainly used at higher integration levels. The approach used in this study involved less spatial scale analysis than earlier multi-scale characterizations and was conducted at the lower scale levels (i.e., region, district and village levels). The results showed that the main constraints to millet production were the low state budgets for investment at the regional and district levels that lead to high prices of inputs and low prices of outputs at the village level. Low soil fertility and high Striga infestation reduce millet production at the village level resulting in a problem of self-sufficiency at the district and regional levels. Surveys conducted at the village level showed that homefields were more fertile than bushfields, because of application of organic manures and animal penning around the village. Only fallows restore the fertility in bushfields representing 99% of the village territory. Millet grain yields and Striga infestation were consistent with these fertility gradients. The results of a 4-years experiment in bushfields indicated that cowpea grown in 1998, had a positive effect on subsequent millet grain yields, soil organic C and N and reduced Striga infestation. The increase in yield due to milletcowpea rotation was 37% in 1999 compared to 3−5 years continuous millet cropping. Including millet/cowpea intercrop in alternative-row configuration after cowpea did not result in significant increase in millet grain yield compared to millet-cowpea rotation in the first and second year, but increased millet grain yields by the third growing season with 22%, the total yields all years and minimized risks of food security in low rainfall years. The effect of intercropping on Striga lasted longer than rotation. The effects of two years fallow on millet grain yield, soil organic C and N and Striga were comparable to those of 5−7 years fallows. P fertilizers enhanced the effects on yield and organic C of both millet sole crop and intercrop with cowpea after a 1-year cowpea crop without significant effect on N and Striga. The model QUEFTS gave a reasonable estimate of nutrient-limited millet yields that can be calculated on the basis of only soil N, P-Bray-I, and exchangeable K. But, validation with input parameters from other millet cropping environments are needed to improve its predictive value for a wide range of environments.

Mots clés : CROP HUSBANDRY / CROP MANAGEMENT / CROP PRODUCTION / SAHEL / AFRICA / MALI

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